Work function tuning of n-channel metal-oxide field-effect transistors using interfacial yttrium layer in fully silicided nickel gate

Abstract

The authors propose to tune the nickel (Ni) fully silicided (FUSI) metal gate work function via an yttrium/Si∕Ni gate stack structure. The work function of such structure indicates that the Y interlayer can effectively tune the Ni FUSI work function from the midgap to the conduction band edge of silicon by controlling the interlayer thickness. The gate stack work function starts to saturate to the pure yttrium value when the yttrium interlayer is >1.6nm. This indicates that the chemical potential of the material adjacent to gate electrode/gate insulator plays an important role in the determination of the work function.